Teeth normally erupt when half to three quarters

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1 ORIGINAL ARTICLE Success rate and of orthodontic treatment for adult patients with palatally impacted maxillary canines Adrian Becker, BDS, LDS, DDO, a and Stella Chaushu, DMD, MSc b Jerusalem, Israel This study was undertaken to examine the success rate and the length of orthodontic treatment of impacted maxillary canines in adult patients. A sample of 19 adults (mean age, years; range, years), who had been treated for a total of 23 impacted maxillary canines, was compared with a younger control group (mean age, years; range, years). The control subjects were chosen for a similar degree of impaction difficulty by carefully matching the positions of the impacted canines in the 3 planes of space. The success rate among the adults was 69.5% compared with 100% among the younger controls. The lower success rate was due to 5 canines that had failed to erupt and 2 canines that had been partially extruded but could not be aligned in the arch. The of treating the overall malocclusion of the adults and young subjects did not materially differ. However, the adults showed significant increases in the and number of treatment visits required for resolving the canine impaction, in both the simpler and the more difficult cases. When further divided by age, all the failed canines were found in the older (over 30) adult subgroup. It was concluded that the prognosis for successful orthodontic resolution of an impacted canine in an adult is lower than that in a younger patient and that the prognosis worsens with age. Furthermore, when such treatment is undertaken, its successful completion should be expected to take considerably longer. (Am J Orthod Dentofacial Orthop 2003;124:509-14) From the Department of Orthodontics, Hebrew University Hadassah School of Dental Medicine, Jerusalem, Israel. a Clinical associate professor. b Clinical senior lecturer. Reprint requests to: Dr Adrian Becker, Clinical Associate Professor, Department of Orthodontics, Hebrew University-Hadassah School of Dental Medicine, PO Box 12272, Jerusalem 91120, Israel; , adrianb@cc.huji.ac.il. Submitted, November 2002; accepted, December Copyright 2003 by the American Association of Orthodontists /2003/$ doi: /s (03)00578-x Teeth normally erupt when half to three quarters of their roots have developed. 1-4 It follows then that teeth with delayed eruption refers to teeth whose roots are more fully developed but are nevertheless expected to erupt spontaneously. Impacted teeth, on the other hand, are teeth whose root development might have finished, but unaided eruption is not expected to occur. 5 Given space to erupt and extraneous means of traction to augment their often-attenuated natural eruptive potential, these teeth will generally erupt and take their place as integral elements in the dentition. Treatment of an impacted maxillary canine needs to be integrated into the overall orthodontic treatment scheme, because (1) space must be prepared for the tooth in the arch, which generally implies moving adjacent teeth, with or without extractions; (2) the other teeth in the same arch and, sometimes, in the mandibular arch must provide the anchorage for the forces applied to the buried tooth to bring it into alignment; and (3) the same appliances will be used both to resolve the impaction and to treat the overall malocclusion, with only minor modifications. Therefore, treating a malocclusion in which there is an impacted canine will take longer than a similar malocclusion in which all the teeth are erupted. 6,7 Most patients seeking and undergoing orthodontic treatment are children or young adults. Impaction of the maxillary canine occurs in approximately 1% to 2% of white populations, 8-10 although this figure appears to be lower among Asians. 11,12 After accurate positional diagnosis of the impacted tooth, the application of light traction forces on the tooth, in the appropriate direction, is almost always followed by positive movement of the tooth, leading to a resolution of the impaction. 5,13-16 It has been a popularly held belief in the past that, among adults, impacted maxillary canines that have been buried for many years might not respond to orthodontic traction and must be extracted. On the other hand, experience has shown that many can be successfully treated in the third, fourth, fifth, even sixth decade of life. Several anecdotal case reports have been published to illustrate treatment of impacted maxillary canines in adults

2 510 Becker and Chaushu American Journal of Orthodontics and Dentofacial Orthopedics November 2003 To our knowledge, no systematic study has been undertaken to examine the relative success rate and length of orthodontic treatment of impacted maxillary canines in adults. Accordingly, this retrospective study was performed to compare these parameters between adult and control populations of patients of orthodontic age. MATERIAL AND METHODS The treatment records of 38 patients with unilateral or bilateral palatally displaced canines were selected from 1 orthodontic practice. This diagnosis was made on the basis of a clinical examination and diagnostic radiographs, according to established standardized methods. 5,20,21 In each patient, the diagnosis was confirmed at the time of surgical exposure by the orthodontist, who was routinely present for this procedure. The experimental group consisted of 19 consecutively treated adults, 7 women and 12 men, having a mean age of years and a range of 20 to 47 years. The control group consisted of 19 matched young patients, 8 girls and 11 boys, with a mean age of years and a range of 12 to 16 years. In each group, 4 patients had bilateral and 15 had unilateral impacted canines. Thus, the total number of impacted canines in each group was 23. The control group of patients was carefully selected from a large number of adolescents with palatally displaced canines, treated in the same clinic. The prerequisite used in matching each adolescent to an adult was a similar position of the impacted canines in the maxilla at the beginning of orthodontic treatment. In the bilateral cases, each canine was matched separately. Impacted maxillary canines vary in their positions in the maxilla and in relation to adjacent teeth, and thus present varying degrees of difficulty with regard to the biomechanical means needed to bring about their successful resolution. Exactly matching the canine positions was mandatory, in order to select control subjects having similar degrees of treatment difficulty and prognoses of therapeutic outcome. The position of each impacted canine was classified according to Becker 5 on the basis of the initial panoramic, cephalometric, and periapical views, and confirmed by the clinical picture at the time of the surgical exposure. This classification system is specifically oriented to assess relative treatment difficulty. The classification refers strictly to palatally displaced maxillary canines and is based on 2 variables: the transverse relationship of the crown of the tooth to the line of the dental arch, which can be close or distant (nearer the midline), and the height of the crown of the tooth in relation to the occlusal plane, which can be defined as high or low. Group 1 canines are in close buccolingual proximity to the line of the arch and are low in the maxilla, with a clear path directly to their ideal place in the arch. Group 2 canines are in close buccolingual proximity to the line of the arch and are low, forward, and mesial to the root of the lateral incisor. They cannot be moved in a direct path to their place in the arch but must be moved in another direction first, to clear the root of the adjacent incisor. Group 3 canines are also in close proximity to the line of the arch but are positioned high in the alveolar bone. Group 4 canines are far from the line of the arch and much closer to the palatal midline and are sited high in the maxilla, usually at some distance from the roots of the incisors. Group 5 canines have their root apices transposed either mesial to the apex of the lateral incisor or distal to the root apex of the first premolar. Group 6 canines are situated in the line of the arch, erupting in place of and resorbing the roots of at least 1 incisor. Of the 23 palatally impacted canines in each group, 9 were classified as group 1, 11 as group 2, and 3 as group 4. None represented groups 3, 5, or 6. The additional selection criteria for inclusion in both groups were: (1) orthodontic treatment provided by the same practitioner and with a similar closederuption surgical technique for exposing the unerupted tooth; (2) regular attendance for orthodontic appointments, as determined from clinical notes; and (3) patient records that included complete diagnostic and treatment notes, pretreatment diagnostically essential radiographic (panoramic, lateral cephalometric, occlusal and periapical) views, banding/bonding date, debanding/debonding date, date of surgical exposure, and date of full engagement of the first stainless steel wire to the impacted canine bracket. The 2 groups were compared in terms of success rate, of comprehensive orthodontic treatment (including number of treatment appointments), and canine treatment (including number of appointments to resolve the canine only). The treatment success rate was assessed on the basis of the posttreatment records. It was defined as successful if treatment was completed to full alignment of the impacted canine in the dental arch; partially successful if the canine was partially extruded (sometimes after surgical luxation) but could not be fully aligned in the dental arch; or failed if the canine could

3 American Journal of Orthodontics and Dentofacial Orthopedics Volume 124, Number 5 Becker and Chaushu 511 Table I. Comparison of adult and young (control) treatment groups with each impacted canine considered separately Age (y; mean SD) F M Successful Partially successful failed Overall tx Number of overall tx appointments Canine tx Number of canine tx appointments Adult (69.5%) 7 (31.5%) group Control group (100%) P.000 NS NS NS (.08) NS NS NS, Not significant; F, female; M, male; tx, treatment. not be moved, presumably due to ankylosis to the surrounding bone. The success rate was calculated as the percentage of successfully aligned canines relative to the total number of canines treated. The whole treatment and number of appointments were calculated from bonding/ banding to debonding/debanding of the fixed appliance. Duration of treatment of the canine and number of appointments were taken from the date of the surgical exposure, at which active traction was applied, to the date the tooth reached the arch and was fully ligated into a stainless steel main archwire. The adult group was initially divided according to age into 2 subgroups, from 20 to 30 years and over 30 years, and the same parameters were compared between each subgroup and the control group. The same parameters were also compared between the group 1 and group 2 canines in the adult group and the controls. Because group 4 was too small to allow statistically meaningful analysis, it was combined with group 2 for further study. The Student t test for paired variables (2-tailed) was used to determine any statistically significant differences (P.05) in treatment and number of appointments between the adult and the adolescent groups. Chi-squared tests were used to determine the significance of differences in the success rate. RESULTS Table I shows the comparisons between the adult and the young (control) groups. The control group started treatment at a mean age of 13.7 years, which was significantly lower (P.0001) than the mean age of the adult group at 29.8 years. The success rate among the adults was 69.5%, compared with 100% among the young controls. The lower success rate was due to 7 unsuccessful cases 5 canines that had failed to erupt and 2 canines that were defined as partially successful, because they had been extruded but could not be aligned in the arch. Of the 5 canines considered failures, 1 was also surgically luxated and subsequently extruded for a small distance, before it stopped again. One canine, considered partially successful, failed to erupt initially, but it was eventually extruded and moved closer to the dental arch after surgical luxation and immediate orthodontic traction. Because of the low numbers involved, the differences in the success rate between the adults and the controls did not reach statistical significance (P.08). There were no significant differences in the overall treatment and number of appointments between the adults and the young patients. Nevertheless, the average treatment period needed to resolve the impacted canine was more than twice as long in the adults than in the controls (12.1 vs 5.5 months). Also, 15.3 (mean) appointments were required to fully align the canine in the successful adult cases compared with 6.9 (mean) appointments in the controls. Both these differences were statistically significant, although the SD was considerable because individual treatment times showed a large range. The part of the orthodontic treatment needed to resolve the impaction in the adults comprised about half of the overall treatment time. In the young controls, involvement with the canine represented about one third of the overall treatment time. Table II summarizes the results when the adults were divided by age into 2 subgroups. The most significant contribution of this subgrouping was to show that all canines that were considered failed or partially failed were in patients over 30 years of age. The success rate for the patients over 30 was 41%, while the success rate in those between 20 and 30 was 100%. Further subdivision of the over-30 group, into a group and an over-40 group, found only 5 canines in the older group. Nevertheless, 4 of the 5 canines that had resisted all efforts to extrude them belonged to this late age group. No significant differences were found in the overall treatment

4 512 Becker and Chaushu American Journal of Orthodontics and Dentofacial Orthopedics November 2003 Table II. Comparison of success rate between subgroups Age subgroup (y) n Successful Partially successful failed Overall tx Number of overall tx appointments Canine tx Number of canine tx appointments (no; mean SD) Adults (100%) Over (41%) 7 (59%) Controls matched to matched to over P, adults 20-29/over NS NS NS NS P, controls matched to NS NS NS NS NS 20-29/over 30 P, adults 20-29/controls NS NS NS NS.04 P, adults over 30/controls.03 NS NS NS, Not significant; tx, treatment. Table III. Comparison of adult and young controls grouped by treatment difficulty Difficulty group n Age (y; mean SD) Successful Partially successful failed Overall tx Number of overall tx appointments Canine tx Number of canine tx appointments (no; mean SD) Adult Control P, adult group1/ NS NS.004 NS (.06) group 2 P, control group1/ NS NS NS NS group 2 P, adult/control group NS NS NS P, adult/control group NS NS NS NS, Not significant; tx, treatment. between the 2 adult subgroups and the controls. Nevertheless, for the canine resolution stage, both adult subgroups needed longer treatment times and more visits than did the young controls. In Table III, the comparisons between the adults and the young controls were performed separately for the simpler group 1 canines and the more difficult group 2 canines. The overall treatment was longer in group 2, but this result reached statistical significance only in the adults. The of treatment and the number of appointments needed to treat the impaction were significantly greater in the group 2 canines, both in the adults and the controls, reflecting the greater treatment difficulty. Although overall treatment time and number of visits were similar in the adult subgroups and the matched control subgroups, the length of treatment and the number of appointments required to resolve the impacted canine were significantly increased in both adult subgroups compared with the controls. DISCUSSION Because palatally impacted canines are frequently associated with only minor malocclusions, 5,22,23 we occasionally encounter patients in whom the impaction has eluded diagnosis until a much later age, when exfoliation of the deciduous canine or, sometimes, a routine examination by the general dentist shows the buried tooth. Alternatively and with the increased demand for orthodontic treatment among adults in recent years, some patients who had strongly opposed orthodontic treatment in adolescence reconsider it later. Adults need to know what level of success can be expected in treating the impacted tooth and the expected of the treatment. Because these cases are relatively rare, most orthodontists have limited

5 American Journal of Orthodontics and Dentofacial Orthopedics Volume 124, Number 5 Becker and Chaushu 513 Fig. A 57-year-old patient with impacted maxillary canine showing extreme replacement resorption of crown of tooth. experience, and a search in the literature is noncontributory because of the lack of published studies performed to answer these questions. A previous study that examined the effect of age at the start of treatment on the of orthodontic treatment in patients with impacted canines found that treatment was longer in younger patients with impacted canines than in an older group. Nevertheless, this study included patients treated in their second decade of life, ie, less than 20 years of age. 7 By and large, the available articles on adult patients are anecdotal case presentations, which give no indication regarding these basic questions. Accordingly, this study aimed to provide information on these 2 issues, by comparing 2 groups of patients who differed only in age. The most important criterion in the careful choice of matched pairs was the initial location of the palatally impacted canines in the 3 planes of spaces. In this context, the retrospective nature of this study was advantageous, because the exact location of the impacted canine was not only determined by the pretreatment radiographic records, but also conclusively confirmed by the orthodontist at the time of the surgical exposure. In addition, the 2 groups were intentionally selected from 1 orthodontic practice and then screened for noncompliant patients, to avoid possible masking of the results due to incompatible operator skills or patient factors. Regarding the success rate, the results showed that among the 23 adult canines, 5 could not be extruded, and 2 could be only partially extruded. Partially successful cases are actually failures in the practical clinical context of day-to-day practice, offering no advantage to the patient in their finally achieved positions. In the young group, all canines were successfully brought into the dental arch. These numbers were too small, relative to the whole group of adults, to yield statistically significant differences when compared with the controls. Nevertheless, with subgrouping by age, the comparison among the success rates in the over-30 subgroup, the subgroup, and the controls became statistically significant, because all the failed or partially failed canines were in this older subgroup. Four of the 5 impacted canines that were considered failures were found in patients over 40 years of age. When the canines were analyzed according to their relative difficulty in treatment, no significant differences in success rates between groups 1 and 2 were found; this suggests that age is the main cause of failure. Matching the initial malocclusions between the 2 groups was not possible, because this would have generated too many factors that required matching. Nevertheless, overall comprehensive treatment was similar between the 2 groups. The portion of the treatment that was concerned with resolving the canine impaction was more than twice as long in the adults and needed a similar increase in the number of visits for adjustment and activation. Although the age-divided adults had different success rates in treatment, the time taken to resolve the aberrant canines, in the successful cases, was similar. As expected when grouped by treatment difficulty, orthodontic resolution of the canine took longer in the more difficult cases, in both the adult and younger groups. Simpler and more difficult canines required longer treatment times and more visits in the adults than in the controls, although this difference was more significant for the more difficult subgroup. However, these findings should be viewed with caution because of the small number of canines that remained in each subgroup after eliminating the failed cases. The present findings support earlier assumptions that teeth that have been impacted for many years undergo pathologic changes that prevent their eruption even when all other factors are favorable. 24 This indicates that the prognosis for a successful orthodontic resolution of an impacted canine in an adult is by no means certain and that it worsens with age. This is presumably due to ankylosis of the impacted tooth to the surrounding bone or, occasionally, actual demonstrable replacement resorption of the crown (Fig). Furthermore, when such treatment is undertaken, its successful completion should be expected to take considerably longer. It becomes evident that, whenever an adult patient presents with an impacted tooth, a calculated risk is

6 514 Becker and Chaushu American Journal of Orthodontics and Dentofacial Orthopedics November 2003 taken in offering orthodontic treatment to resolve the impaction. The patient should be informed of the possibility of failure, a factor that, together with the increased treatment time, must be brought into the decision-making process from the outset. REFERENCES 1. Nolla CM. The development of permanent teeth. J Dent Child 1960;27: Moorrees CFA, Fanning EA, Grøn AM, Lebret L. The timing of orthodontic treatment in relation to tooth formation. Trans Eur Orthod Soc 1962;38: Moorrees CFA, Fanning EA, Hunt EE Jr. Age variation of formation stages for ten permanent teeth. J Dent Res 1963;42: Koyoumdjisky-Kaye E, Baras M, Grover NB. Stages in the emergence of the dentition: an improved classification and its application to Israeli schoolchildren. Growth 1977;41: Becker A. The orthodontic treatment of impacted teeth. London: Martin Dunitz Ltd; Iramaneerat S, Cunningham SJ, Horrocks EN. The effect of two alternative methods of canine exposure upon subsequent of orthodontic treatment. Int J Paediatr Dent 1998;8: Stewart JA, Heo G, Glover KE, Williamson PC, Lam EW, Major PW. Factors that relate to treatment for patients with palatally impacted maxillary canines. Am J Orthod Dentofacial Orthop 2001;119: Dachi SF, Howell FV. A survey of 3874 routine full-mouth radiographs II. A study of impacted teeth. Oral Surg Oral Med Oral Pathol 1961;14: Thilander B, Jacobson SO. Local factors in impaction of maxillary canines. Acta Odontol Scand 1968;26: Brin I, Becker A, Shalhav M. Position of the maxillary permanent canine in relation to anomalous or missing lateral incisors. Eur J Orthod 1986;8: Takahama Y, Aiyama Y. Maxillary canine impaction as a possible microform of cleft lip and palate. Eur J Orthod 1982;4: Oliver RG, Mannion JE, Robinson JM. Morphology of the maxillary lateral incisor in cases of unilateral impaction of the maxillary canine. Br J Orthod 1989;16: Becker A, Zilberman Y. The palatally impacted canine: a new approach to its treatment. Am J Orthod 1978;74: Jacoby H. The ballista spring system for impacted teeth. Am J Orthod 1979;75: Kornhauser M, Abed Y, Harari D, Becker A. The resolution of palatally impacted canines using a palato-occlusion force from a buccal auxiliary. Am J Orthod Dentofacial Orthop 1995;110: Orton HS, Garvey MT, Pearson MH. Extrusion of the ectopic maxillary canine using a lower removable appliance. Am J Orthod Dentofacial Orthop 1995;107: Zuccati G. Bilaterally impacted maxillary canines: a case report in an adult. Eur J Orthod 1994;16: Cureton SL, Polk LM. Class II Division 1 case with multiple treatment challenges. Am J Orthod Dentofacial Orthop 1999; 115: Frank CA, Long M. Periodontal concerns associated with the orthodontic treatment of impacted teeth. Am J Orthod Dentofacial Orthop 2002;121: Seward GR. Radiology in general dental practice. IX-unerupted maxillary canines, central incisors and supernumeraries. Br Dent J 1963;115: Hunter SB. The radiographic assessment of the unerupted maxillary canine. Br Dent J 1981;150: Jacoby H. The etiology of maxillary canine impaction. Am J Orthod 1983;84: Becker A. Etiology of maxillary canine impactions. Am J Orthod 1984;86: Azaz B, Shteyer A. Resorption of the crown in impacted maxillary canine. A clinical, radiographic and histological study. Int J Oral Surg 1978;7: AVAILABILITY OF JOURNAL BACK ISSUES As a service to our subscribers, copies of back issues of the American Journal of Orthodontics and Dentofacial Orthopedics for the preceding 5 years are maintained and are available for purchase from Mosby until inventory is depleted. Please write to Mosby, Subscription Customer Service, 6277 Sea Harbor Dr, Orlando, FL 32887, or call or for information on availability of particular issues and prices.